1. Field of the Invention
The present invention relates to an automotive alternator and particularly to a stator winding construction for an automotive alternator.
2. Description of the Related Art
Generally, an automotive alternator includes: a stator constructed by installing a stator winding into a cylindrical stator core in which slots extending axially are formed at a predetermined pitch in a circumferential direction; and a rotor disposed on an inner circumferential side of the stator and having a field winding. The slots are disposed in the stator core at a ratio of one per phase per pole, in proportion to the number of phases in the stator winding and the number of magnetic poles in the rotor.
When the slots are disposed at a ratio of one per phase per pole in this manner, the amount of time that a tooth formed between the slots overlaps an adjacent pair of the magnetic poles.relative to a radial direction is long, leading to increased magnetic flux leakage. This magnetic flux leakage reduces effective magnetic flux and gives rise to surges in the magnetic flux, resulting in fluctuations in the generated voltage and disturbing the output waveform, which causes ripples when the alternating current is converted into direct current.
Thus, an attempt has been proposed in Japanese Patent Laid-Open No. HEI 4-26345, for example, to reduce magnetic flux leakage by disposing the slots at a ratio of two per phase per pole to shorten the amount of time that a tooth overlaps an adjacent pair of the magnetic poles relative to the radial direction.
FIG. 20 is a schematic diagram in which part of a stator such as that described in Japanese Patent Laid-Open No. HEI 4-26345, for example, is developed into a plan.
In FIG. 20, a stator core 60 is composed by forming a magnetic steel plate into a cylindrical shape, slots 61 extending axially being disposed therein at an even angular pitch in a circumferential direction at a ratio of two per phase per pole. Here, for twelve magnetic poles in a rotor (not shown), seventy-two slots 61 are disposed in the stator core 60 so as to obtain a stator winding 63 composed of first and second three-phase alternating-current windings. The seventy-two slots 61 are constructed by arranging at a pitch of six slots slot group composed of first to sixth slots 61a, 61axe2x80x2, G1b, 61bxe2x80x2, 61c, and 61cxe2x80x2 disposed at a pitch corresponding to an electrical angle of 30xc2x0 from each other.
A first single-phase winding portion 63a is constructed by winding a conductor wire into a wave shape in a first slot group composed of the first slots 61a, a third single-phase winding portion 63b is constructed by winding a conductor wire into a wave shape in a third slot group composed of the third slots 61b, and in addition, a fifth single-phase winding portion 63c is constructed by winding a conductor wire into a wave shape in a fifth slot group composed of the fifth slots 61c. The first three-phase alternating-current winding is constructed by forming the first, third, and fifth single-phase winding portions 63a, 63b, and 63c wound in this manner into a Y-connection. Here, the slots into which the first, third, and fifth single-phase winding portions 63a, 63b, and 63c are wound have a phase difference corresponding to an electrical angle of 60xc2x0 from each other.
A second single-phase winding portion 63axe2x80x2 is constructed by winding a conductor wire into a wave shape in a second slot group composed of the second slots 61axe2x80x2, a fourth single-phase winding portion 63bxe2x80x2 is constructed by winding a conductor wire into a wave shape in a fourth slot group composed of the fourth slots 61bxe2x80x2, and in addition, a sixth single-phase winding portion 63cxe2x80x2 is constructed by winding a conductor wire into a wave shape in a sixth slot group composed of the sixth slots 61cxe2x80x2. The second three-phase alternating-current winding is constructed by forming the second, fourth, and sixth single-phase winding portions 63axe2x80x2, 63bxe2x80x2, and 63cxe2x80x2 wound in this manner into a Y-connection. Here, the slots into which the second, fourth, and sixth single-phase winding portions 63axe2x80x2, 63bxe2x80x2, and 63cxe2x80x2 are wound have a phase difference corresponding to an electrical angle of 60xc2x0 from each other. Furthermore, the second, fourth, and sixth single-phase winding portions 63axe2x80x2, 63bxe2x80x2, and 63cxe2x80x2 have a phase difference corresponding to an electrical angle of 30xc2x0 from the first, third, and fifth single-phase winding portions 63a, 63b, and 63c, respectively.
As shown in FIG. 21, a stator 65 is prepared by winding these single-phase winding portions 63a, 63axe2x80x2, 63b, 63bxe2x80x2, 63c, and 63cxe2x80x2 in the stator core 60. In the stator 65 constructed in this manner, because the slots 61 are disposed at a ratio of two per phase per pole, portions of a tooth 62 overlapping an adjacent pair of the magnetic poles relative to the radial direction is dramatically reduced. Thus, magnetic flux leakage is reduced, enabling reductions in effective magnetic flux to be suppressed. Similarly, the generation of surges in the magnetic flux is suppressed, reducing fluctuations in the generated voltage and disturbances to the output waveform, thereby reducing ripples when the alternating current is converted into direct current.
In the stator 65 of the conventional automotive alternator, as explained above, the single-phase winding portions 63a, 63axe2x80x2, 63b, 63bxe2x80x2, 63c, and 63cxe2x80x2 constituting the stator winding 63 are each constructed by winding the conductor wire into a wave shape in every sixth slot 61 so as to extend out of a first slot 61 and enter a second slot 61 six slots away.
As shown in FIG. 22, bundles containing a predetermined number of the conductor wires constituting the single-phase winding portions 63a, 63axe2x80x2, 63b, 63bxe2x80x2, 63c, and 63cxe2x80x2 overlap radially in regions A where the conductor wires are bent circumferentially after extending outwards from the slots 61, expanding radially.
Thus, coil end groups of the stator winding 63 are formed with large irregularities relative to the circumferential direction, and one problem has been that loud wind noise is generated as a result of pressure differences between the coil end groups and the rotor and between the coil end groups and fans. Furthermore, the radially-overlapping bundles of the conductor wires in the regions A where the conductor wires are bent circumferentially after extending outwards from the slots 61 are less likely to be exposed to a cooling airflow, and therefore another problem has been that heat generated in the stator 65 does not efficiently dissipate from the coil end groups, making it difficult to suppress temperature increases in the stator 65, and output cannot be improved.
Thus, in a conventional automotive alternator mounted with the stator 65 in which the two three-phase alternating-current windings are wound into the stator core 60 in which slots are disposed at a ratio of two per phase per pole, there have been problems preventing increased performance from the viewpoints of wind noise and output.
The present invention aims to solve the above problems and an object of the present invention is to provide an automotive alternator enabling temperature increases in a stator to be suppressed by constructing a single-phase winding portion constituting a stator winding by installing a conductor wire which extends from slots such that winds thereof are divided onto first and second circumferential sides, reducing circumferential irregularities in a coil end group to reduce wind noise, and suppressing radial overlap between bundles of winds of the conductor wire constituting the coil end group to raise heat dissipation from the coil end group.
In order to achieve the above object, according to one aspect of the present invention, there is provided an automotive alternator including:
a rotor rotatably supported in a bracket; and
a stator provided with a cylindrical stator core in which a plurality of slots extending axially are formed circumferentially and a stator winding installed in the stator core, the stator being supported in the bracket so as to surround an outer circumference of the rotor,
wnerein the slots are formed in the stator core at a ratio of two per phase per pole,
wherein the stator winding is provided with two three-phase alternating-current windings, each of the three-phase alternating-current windings being constructed by forming three single-phase winding portions installed in the slots into an alternating-current connection, and
wherein each of the single-phase winding portions is constructed by installing a conductor wire such that winds of the conductor wire extend outwards from first and second ends of the slots, are divided onto first and second circumferential sides, and enter slots on the first and second circumferential sides.
At least one of the single-phase winding portions may be provided with a plurality of wave windings formed by winding the conductor wire for a predetermined number of winds into a wave-shaped pattern composed of slot-housed portions disposed at a pitch of six slots in a circumferential direction and crossover portions linking together end portions of adjacent pairs of the slot-housed portions alternately relative to an axial direction,
the plurality of wave windings being offset by six slots from each other in a circumferential direction and installed in the slots such that the crossover portions face each other axially.
At least one of the single-phase winding portions may be provided with a divided wave winding, the divided wave winding including:
a first winding sub-portion formed by winding the conductor wire for a predetermined number of winds into a first wave-shaped pattern composed of first slot-housed portions disposed at a pitch of six slots in a circumferential direction and first crossover portions linking together end portions of adjacent pairs of the first slot-housed portions alternately relative to an axial direction; and
a second winding sub-portion formed by continuing to wind the conductor wire from a winding finish end of the first winding sub-portion for a predetermined number of winds into a second wave-shaped pattern composed of second slot-housed portions disposed at a pitch of six slots in a circumferential direction and second crossover portions linking together end portions of adjacent pairs of the second slot-housed portions alternately relative to an axial direction,
wherein the first winding sub-portion and the second winding sub-portion are stacked such that the first slot-housed portions and the second slot-housed portions face each other, and the first crossover portions and the second crossover portions face each other axially.
A neutral-point lead wire of at least one of the single-phase winding portions may be led out of a first slot and an output wire thereof may be led out of a second slot.
At least one of the three-phase alternating-current windings may be constructed by forming the three single-phase winding portions into a Y-connection, slots out of which neutral-point lead wires of the three single-phase winding portions are led being disposed between a circumferentially-adjacent pair of slots out of which output wires of the single-phase winding portions are led.
At least one of the single-phase winding portions may be constructed by installing the conductor wire in a lap winding in the slots.
At least one of the single-phase winding portions may be provided with a winding sub-portion constructed by simultaneously winding a plurality of strands of the conductor wire.
At least one of the single-phase winding portions may be constructed by connecting in series winding sub-portions constructed by winding the conductor wire.
The number of divided winds of the conductor wire extending outwards from the first and second ends of the slots and divided onto the first and second circumferential sides may be the same in at least one of the single-phase winding portions.
At least one of the single-phase winding portions may be provided with a plurality of winding sub-portions formed by installing at least one strand of the conductor wire in the stator core, the number of divided winds of the conductor wire extending outwards from the first and second ends of the slots and divided onto the first and second circumferential sides being different in each of the plurality of winding sub-portions, and the total number of divided winds of the conductor wire extending outwards from the first and second ends of the slots and divided onto the first and second circumferential sides being the same on the first and second circumferential sides.
Coil end groups of the stator winding may be constituted by a plurality of crossover portions linking together slot-housed portions of the conductor wire housed in pairs of the slots six slots apart outside end surfaces of the stator core, at least some crossover portions of the plurality of crossover portions being axially offset.
Coil end groups of the stator winding may be constituted by a plurality of crossover portions linking together slot-housed portions of the conductor wire housed in pairs of the slots six slots apart outside end surfaces of the stator core, the crossover portions constituting an inner circumferential side of the coil end groups being constructed such that the winds of the conductor wire therein line up axially without overlapping radially.
A fan may be mounted to an axial end surface of the rotor; and
coil end groups of the stator winding may be constituted by a plurality of crossover portions linking together slot-housed portions of the conductor wire housed in pairs of the slots six slots apart outside end surfaces of the stator core,
wherein the axial end surface of the rotor to which the fan is mounted is positioned axially outside base portions of the crossover portions.
A fan may be mounted to an axial end surface of the rotor; and
coil end groups of the stator winding may be constituted by a plurality of crossover portions linking together slot-housed portions of the conductor wire housed in pairs of the slots six slots apart outside end surfaces of the stator core,
wherein the fan and the crossover portions overlap relative to an axial direction, and
wherein a ventilation gap is formed between base portions of the crossover portions and end surfaces of the stator.
A central portion of an axial height of the fan and an apex portion of the coil end group may be generally aligned relative to the axial direction.